//package com.example.studyproject.distributeId;
//
//import java.net.NetworkInterface;
//import java.util.Enumeration;
//import java.util.Random;
//import java.util.concurrent.atomic.AtomicLong;
//
///**
// * @program: StudyProject
// * @description:
// * @author: kangwei
// * @create: 2025-05-09 13:56
// **/
//public class IdWorker {
//    /**
//     * Start time cut (2020-05-03)
//     */
//    private final long twepoch = 1588435200000L;
//
//    /**
//     * The number of bits occupied by workerId
//     */
//    private final int workerIdBits = 10;
//
//    /**
//     * The number of bits occupied by timestamp
//     */
//    private final int timestampBits = 41;
//
//    /**
//     * The number of bits occupied by sequence
//     */
//    private final int sequenceBits = 12;
//
//    /**
//     * Maximum supported machine id, the result is 1023
//     */
//    private final int maxWorkerId = ~(-1 << workerIdBits);
//
//    /**
//     * business meaning: machine ID (0 ~ 1023)
//     * actual layout in memory:
//     * highest 1 bit: 0
//     * middle 10 bit: workerId
//     * lowest 53 bit: all 0
//     */
//    private long workerId;
//
//    /**
//     * timestamp and sequence mix in one Long
//     * highest 11 bit: not used
//     * middle  41 bit: timestamp
//     * lowest  12 bit: sequence
//     */
//    private AtomicLong timestampAndSequence;
//
//    /**
//     * mask that help to extract timestamp and sequence from a long
//     */
//    private final long timestampAndSequenceMask = ~(-1L << (timestampBits + sequenceBits));
//
//    /**
//     * instantiate an IdWorker using given workerId
//     * @param workerId if null, then will auto assign one
//     */
//    public IdWorker(Long workerId) {
//        initTimestampAndSequence();
//        initWorkerId(workerId);
//    }
//
//    /**
//     * init first timestamp and sequence immediately
//     */
//    private void initTimestampAndSequence() {
//        long timestamp = getNewestTimestamp();
//        long timestampWithSequence = timestamp << sequenceBits;
//        this.timestampAndSequence = new AtomicLong(timestampWithSequence);
//    }
//
//    /**
//     * init workerId
//     * @param workerId if null, then auto generate one
//     */
//    private void initWorkerId(Long workerId) {
//        if (workerId == null) {
//            workerId = generateWorkerId();
//        }
//        if (workerId > maxWorkerId || workerId < 0) {
//            String message = String.format("worker Id can't be greater than %d or less than 0", maxWorkerId);
//            throw new IllegalArgumentException(message);
//        }
//        this.workerId = workerId << (timestampBits + sequenceBits);
//    }
//
//    /**
//     * get next UUID(base on snowflake algorithm), which look like:
//     * highest 1 bit: always 0
//     * next   10 bit: workerId
//     * next   41 bit: timestamp
//     * lowest 12 bit: sequence
//     * @return UUID
//     */
//    public long nextId() {
//        waitIfNecessary();
//        long next = timestampAndSequence.incrementAndGet();
//        long timestampWithSequence = next & timestampAndSequenceMask;
//        return workerId | timestampWithSequence;
//    }
//
//    /**
//     * block current thread if the QPS of acquiring UUID is too high
//     * that current sequence space is exhausted
//     */
//    private void waitIfNecessary() {
//        long currentWithSequence = timestampAndSequence.get();
//        long current = currentWithSequence >>> sequenceBits;
//        long newest = getNewestTimestamp();
//        if (current >= newest) {
//            try {
//                Thread.sleep(5);
//            } catch (InterruptedException ignore) {
//                // don't care
//            }
//        }
//    }
//
//    /**
//     * get newest timestamp relative to twepoch
//     */
//    private long getNewestTimestamp() {
//        return System.currentTimeMillis() - twepoch;
//    }
//
//    /**
//     * auto generate workerId, try using mac first, if failed, then randomly generate one
//     * @return workerId
//     */
//    private long generateWorkerId() {
//        try {
//            return generateWorkerIdBaseOnMac();
//        } catch (Exception e) {
//            return generateRandomWorkerId();
//        }
//    }
//
//    /**
//     * use lowest 10 bit of available MAC as workerId
//     * @return workerId
//     * @throws Exception when there is no available mac found
//     */
//    private long generateWorkerIdBaseOnMac() throws Exception {
//        Enumeration<NetworkInterface> all = NetworkInterface.getNetworkInterfaces();
//        while (all.hasMoreElements()) {
//            NetworkInterface networkInterface = all.nextElement();
//            boolean isLoopback = networkInterface.isLoopback();
//            boolean isVirtual = networkInterface.isVirtual();
//            byte[] mac = networkInterface.getHardwareAddress();
//            if (isLoopback || isVirtual || mac == null) {
//                continue;
//            }
//            return ((mac[4] & 0B11) << 8) | (mac[5] & 0xFF);
//        }
//        throw new RuntimeException("no available mac found");
//    }
//
//    /**
//     * randomly generate one as workerId
//     * @return workerId
//     */
//    private long generateRandomWorkerId() {
//        return new Random().nextInt(maxWorkerId + 1);
//    }
//}
